Rotary toothbrushes have been contemplated in the past with complicated mechanisms such as U.S. Pat. Nos. 1,949,241 and 3,241,169.
Simplified mechanical arrangements were described by L. Bercovitz in Canadian Pat. No. 709,542 corresponding to U.S. Pat. No. 3,214,776. Bercovitz relies on a handle made of a one-piece bow member as crank arm to oscillate the toothbrush.